Students determine the saturation temperature of 5 solutions of ammonium chloride, plot a solubility curve, and use the curve to predict ammonium chloride's solubility at any temperature on the curve. Students study the properties of solutions, the effect of temperature on solubility, and the phenomenon of supersaturated solutions. In addition, students observe physical changes as they dissolve and recrystallize the salt. Each trial is repeated for accuracy and to reinforce the importance of repeatable results. Unlike traditional solubility experiments that use ammonium nitrate, this experiment uses ammonium chloride, a much greener choice. Materials are sufficient for 30 students working in pairs.